Medical imaging and extraction of anatomy from imaging is important, as evidenced by the many means of medical imaging available. Common forms of medical imaging include computed tomography (CT) scans, magnetic resonance imaging, intravascular ultrasound, intravascular optical coherence tomography, angiography, and histopathology optical images. CT scans are x-ray images of “slices” of a scanned object. For example, CT scans are commonly images taken as cross-sectional slices, perpendicular to the long axis of the body. Cardiac CT scans may include calcium-score screening and/or angiography. Calcium score screening scans may be used to detect calcium deposits in coronary arteries, contributing to predictions of heart problems. CT angiography is CT scanning including intravenous (IV) contrast dye to better show blood vessels and organs. Although also capable of producing tomographic images, magnetic resonance (MR) imaging uses magnetic field properties to create the images. Because CT and MRI images are produced differently, resultant images highlight different tissue properties. MR images offer better quality in soft tissue images than CT scans; CT scans image bone and blood vessels in addition to soft tissue, although the soft tissue detail is inferior to that of MR images. Depending on the anatomy of interest and purpose of imaging, CT and MR may be considered complimentary imaging techniques.
Intravascular ultrasound (IVUS) is a type of imaging that visualizes the inside of blood vessels. Whereas CT and MR methods involve images taken as slices of a patient body, IVUS images are achieved via a catheter traveling through an artery or vein. Thus, IVUS images may essentially show cross-sections of the artery or vein, from the center of a blood vessel, out through the vessel wall and whatever diseased portion may exist at the wall. Intravascular optical coherence tomography (OCT) is an optical analog of the ultrasound imaging of IVUS. IVUS and OCT are analogous imaging modalities, but OCT's use of light (in place of sound) offers higher resolution images than IVUS. Briefly discussed in the context of CT scans, angiography is an imaging technique that employs an injection of a contrast agent into the blood stream to better show vessels or vessel openings. While CT angiography may be preferable for coronary disease detection, MR angiography is a viable alternative. Histopathological optical imaging includes visualization of tissue on a microscopic level. Histopathological imaging can be used to identify tissue or detect for various biomarkers. One common prerequisite for the analysis of histopathological images is the localization of cells, tissue or other anatomical and cellular objects within the images.
Based on images from techniques described above, anatomical models may be extracted to measure one or more properties of a patient's anatomy (e.g., a tumor or cardiac volume) or to support biophysical simulation (e.g., fluid simulation, biomechanical simulation, electrophysiological simulation, etc.). In order to accurately measure anatomical properties or predict physiological phenomena via simulation, a very precise patient-specific model must be created of the target anatomy. Imaging and subsequent extraction of anatomical models of the heart, for example, is of special importance. For instance, such imaging and modeling may provide evaluation of coronary artery disease, such as when a patient is suffering from chest pain, and/or a more severe manifestation of disease, such as myocardial infarction, or heart attack.
Patients suffering from chest pain and/or exhibiting symptoms of coronary artery disease may be subjected to one or more tests that may provide some indirect evidence relating to coronary lesions. For example, noninvasive tests may include electrocardiograms, biomarker evaluation from blood tests, treadmill tests, echocardiography, single positron emission computed tomography (SPECT), and positron emission tomography (PET). These noninvasive tests, however, typically do not provide a direct assessment of coronary lesions or assess blood flow rates. The noninvasive tests may provide indirect evidence of coronary lesions by looking for changes in electrical activity of the heart (e.g., using electrocardiography (ECG)), motion of the myocardium (e.g., using stress echocardiography), perfusion of the myocardium (e.g., using PET or SPECT), or metabolic changes (e.g., using biomarkers). For example, anatomic data may be obtained noninvasively using coronary computed tomographic angiography (CCTA). CCTA may be used for imaging of patients with chest pain and involves using CT technology to image the heart and the coronary arteries following an intravenous infusion of a contrast agent.
However, single images may be insufficient to create ideal models. The foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.